Children with a history of trauma and posttraumatic stress disorder (PTSD) have been shown to have significantly higher heart rate reactivity following exposure to personal trauma related stimuli as compared to children without PTSD (Perry, 1994; Saltzman et al., 2005). Studies have also found that trauma-exposure in youth is associated with reactive aggression but not proactive aggression. Together these findings suggest that physiological reactivity and perception of threat might be related to the higher rates of aggression and delinquency reported among trauma- exposed youth. The sympathetic activity of the cardiovascular system is central to the fight-flight response that is often activatd by appraisals of threat. This system has been shown to be over-active in adults with PTSD. However, few studies have examined autonomic and neuroendocrine reactivity to acute stress and provocation among adolescents with a history of trauma exposure and post trauma symptoms. The proposed research takes a multi-system approach, examining physiological stress reactivity and reactive aggression among 14 to 19 year-old youth, primarily African American and Latino youth. At completion the findings will further our understanding of the developmental aspects of stress and trauma response. A greater understanding of the effects of stress and trauma on development is particularly important for minority youth given the disproportionate rates of trauma exposure and trauma symptoms reported in the extant literature.